<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        window.onload=function(){
            var oUl=document.getElementById('ul1');
            alert(oUl.parentNode);
        };
    </script>
</head>
<body>
<ul id="ul1">
    <li></li>
    <li></li>
</ul>
</body>
</html>